1. Field of the Invention
The present invention relates to a heat exchanger with a plurality of tube sheets stacked in layers.
2. Description of Related Art
A known heat exchanger has a plurality of flat tubes stacked in layers. In such a heat exchanger, each flat tube has a coolant passage extending in a longitudinal direction and a cylindrical tank protruding in the stacking direction from each side of each longitudinal end of the coolant passage. The tanks of the stacked flat tubes are joined to form a header tank.
Each flat tube consists of two tube sheets that are arranged face to face and are joined together. Each tube sheet has a flat part, a recess part that is depressed from the flat part to form the coolant passage of the flat tube when joined with a counterpart tube sheet, and a cylindrical tank that protrudes from each longitudinal end of the recess part to serve as the tank of the flat tube.
The heat exchanger must form therein a route for passing a coolant. For this, a modified tube sheet is arranged at a predetermined location in the heat exchanger. The modified tube sheet has a modified tank that is different from a normal tank provided for a normal tube sheet. The modified tank has a partition to close an opening of the tank, or a throttle to reduce the opening of the tank. Such a modified tube sheet with a modified tank has the same or similar external shape as the normal tube sheet. It is difficult, therefore, to identify, from an external view of the heat exchanger, the modified tube sheets from among the stacked tube sheets of the heat exchanger. To solve the problem, Japanese Unexamined Patent Application Publication No. Hei-9-152294 discloses a heat exchanger that puts a mark such as a rib or a notch on a modified tube sheet. This heat exchanger allows a person to identify, from an external view of the heat exchanger, the modified tube sheet in the heat exchanger.